1. Field of the Invention:
This invention relates to cameras, and more particularly to improvements in a blank film advance control device for automatically initiating a blank film advancing operation in response to insertion of a film cartridge into the camera followed by closure of the back cover.
2. Description of the Related Art:
In conventional cameras having the function of automatically advancing blank film, the coordination of the device therefor and the film cartridge chamber cover, or the back cover of the camera, has generally been controlled in such a manner that after the film cartridge has been inserted into the chamber, when the back cover is closed, the film is automatically advanced, for example, four frames, and thereby the camera is readied for taking photographs. The use of such coordination control has the disadvantage that even when the photographer carelessly re-opens the back cover after the camera had been loaded with film to the end of blank advance, the re-closure of the back cover actuates the blank film advance device to operate again in exactly the same manner. Thus, the blank film advance is recycled. Therefore, many drawbacks such as those discussed below have arisen.
For example, the automatic transition from the wind to the rewind mode has recently found increasing use in cameras. For example, as a definite number of frames have been exposed, the film gets stopped from further advancing, this film stoppage is detected to automatically initiate a film rewinding operation. If this function were left effective even before the start of the blank film advance, failure of the blank film advance (i.e., such that the film leader is out of engagement on the takeup spool) would cause the film to move backward with the result that the film leader is all pulled into the cartridge. So, the film could no longer be used, while being left unexposed. To eliminate this problem, the prior art made a provision that automatic transition to the rewind mode is prevented from occurring before the end of the blank film advance.
In application of this technique to the conventional type camera in which the blank film advance is recycled each time the back cover is opened and closed, when the back cover is accidentally re-opened and re-closed after the end of the blank film advance as mentioned above, but just before the end of the film (the remaining number of fresh frames is, for example, three or less), it is unavoidable that the film is tensioned in the middle course of the second cycle of the blank film advancing operation, nevertheless the automatic function of switching the camera from the wind to the rewind mode does not work. In this case, therefore, the photographer has to rewind the film manually. This is very troublesome.
Another drawback arising from the possibility of recycling the blank film advance is that the frames which would otherwise be usable for taking photograph are advanced in vain. Thus, the use of the prior known coordination control of the blank film advance device with the back cover of the camera led to many serious problems.